feat(dictionary): add Hachidori backend support

- Add backend selection, setup gating, Anki integration, and external host support
- Add launcher flags, documentation, packaging, and focused tests
- Open on-demand overlay modals on the first attempt

src/config/resolve/dictionary-backend.test.ts

@@ -0,0 +1,30 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import { resolveConfig } from '../resolve';
+import { buildConfigSettingsRegistry } from '../settings/registry';
+import { createResolveContext } from './context';
+import { applyCoreDomainConfig } from './core-domains';
+
+test('dictionary backend defaults to Yomitan and accepts Hachidori', () => {
+  assert.equal(resolveConfig({}).resolved.dictionaryBackend, 'yomitan');
+  const { resolved, warnings } = resolveConfig({ dictionaryBackend: 'hachidori' });
+  assert.equal(resolved.dictionaryBackend, 'hachidori');
+  assert.deepEqual(warnings, []);
+  const field = buildConfigSettingsRegistry(resolved).find(
+    (entry) => entry.configPath === 'dictionaryBackend',
+  );
+  assert.equal(field?.restartBehavior, 'restart');
+  assert.deepEqual(field?.enumValues, ['yomitan', 'hachidori']);
+  assert.equal(field?.category, 'integrations');
+});
+
+test('unknown dictionary backend values warn and preserve the default', () => {
+  for (const dictionaryBackend of ['unknown', '', null, true, {}]) {
+    const { context, warnings } = createResolveContext({});
+    context.src.dictionaryBackend = dictionaryBackend;
+    applyCoreDomainConfig(context);
+    assert.equal(context.resolved.dictionaryBackend, 'yomitan');
+    assert.equal(warnings.length, 1);
+    assert.equal(warnings[0]?.path, 'dictionaryBackend');
+  }
+});